对某核电站稳压器电加热元件的包壳管变色原因进行了分析。结果表明:不锈钢包壳管长期暴露在高温环境中,其表面生成了均匀、致密的保护性氧化膜,氧化膜颗粒细小;变色包壳管材料不同部位的晶粒度均为6.5~7级,未出现晶粒异常长大的现象,非金属夹杂物和α相含量无异常;包壳管与端塞处焊缝未观察到裂纹。

The discoloration reason of the cladding tube of the electrical heating element of a nuclear power plant regulator was analyzed. The results show that uniform and dense protective oxide film was formed on the surface of stainless steel cladding tube exposed to high temperature for a long time, and the oxide film particles were fine. The grain size of different parts of the discoloration cladding tube material was 6. 5~7 grade, and there was no abnormal grain growth, and there was no abnormal content of non-metallic inclusions and α phase. No cracks were observed in the weld between the cladding tube and the end plug.